I went to a lecture in the 90s that some ILM guys were speaking at and one of them said the garbage mattes were dependent on the color timing of each particular print, which varied wildly (and got worse as prints aged and faded back in the days of movies playing in theaters for months/years). Which drove Lucas crazy and helped make him yearn for digital projection where the movie would look the same no matter when and where you saw it. You can also see Spielberg on some interview talking about how "on a bad print" the Raiders cobra reflection is really noticeable. I saw a very good print of Raiders recently and yeah it's there if you are looking, but it's not even close to how noticeable it was on the vhs/laserdisc.